The present invention relates to a misalignment prevention device in a copy-paper transport, and more particularly, to a device that prevents transport of copy paper whenever a condition exists in the transport operation that may jam the copy paper.
Conventional electrophotographic copying machines transport copy paper to the image generator, which forms pictures on the paper before ejecting it from the copying machine. Copy paper is transported to the image generator through the copy-paper transport path by means of conveyer rollers. Conventional copiers provide methods of detection, such as microswitches, which sense the position and condition of paper in the paper-transport path. In response to the information gathered from microswitches, the drive train of the conveyer rollers is modified so that copy papers can be securely and correctly transported to the image generator. In most copy machines, each copy paper should pass through a monitoring device within a specified period of time, but if the designated copy paper doesn't pass through the monitor within a predetermined time, the device records that the copy paper has been fed incorrectly and jamming has occurred along the transport path. In that situation all the operations of the conveyer roller and copying machine are suspended until the jam has been rectified. Some conventional copying machines or printers are designed to transport copy papers by examining only one edge of the paper to ensure proper alignment. Unless copy papers are correctly transported with their edge precisely aligned with a reference edge monitor however, copy papers may jam in transit or pictures and characters may be incorrectly copied or printed. To prevent this, conventional copying machines and printers employ a paper detection device at the reference edge of the paper-transport path to sense whether copy papers are being correctly transported. Nevertheless, conventional copying machines and printers are designed to identify whether copy papers have been correctly transported only after copy papers have actually passed through the paper-position monitors. Because of this, conventional copy machines and printers cannot effectively prevent the incorrectly aligned papers from being carried beyond the paper-position monitors and into conveyer rollers. This disadvantage is also present in copiers which utilize monitors in the center of the copy path to detect alignment.